This invention relates to a system for transporting genes into eukaryotic cells. More particularly, the invention relates to a composition and a method for delivering a selected nucleic acid into a host cell using a biodegradable, mixed polymeric micelle comprising an amphiphilic polyester-polycation copolymer and an amphiphilic polyester-sugar copolymer.
Early efforts to identify methods of delivering nucleic acids into tissue culture cells began in the mid-1950's. H. E. Alexander et al., 5 Virology 172-173 (1958). Since then, steady progress has been made toward improving delivery of functional DNA, RNA, and antisense oligonucleotides (RNA function inhibitors) in vitro and in vivo. Substantial progress has been achieved during the last two decades due to the convergence of transfection technology and recombinant DNA technology in the late 1970's. This convergence began when calcium phosphate and diethylaminoethyldextran were applied for the expression of recombinant plasmids in cultured mammalian cells. P. J. Southern et al., 1 J. Mol. Appl. Gen. 327-341 (1982). Presently, delivery and expression of nucleic acids has become a topic that continues to capture scientific attention.
Some success has been achieved in delivering functional, non-replicating plasmids in vitro, however, the current methods for delivering functional, non-replicating plasmids in vivo are in their infancy. Transfection techniques include methods using insoluble inorganic salts, F. Graham, 52 Virology 456-462 (1973), cationic lipids, E. R. Lee et al., 7 Human Gene Therapy 1701-1717 (1996), cationic polymers, B. A. Demeneix et al., 7 Human Gene Therapy 1947-1954 (1996); A. V. Kabanov et al., 6 Bioconjugate Chem. 7-20 (1995); E. Wagner, 88 Proc. Natl. Acad. Sci. USA 4255-4259 (1991), viral vectors, A. H. Jobe, 7 Human Gene Therapy 697-704 (1996); J. Gauldie, 6 Current Opinion in Biotechnology 590-595 (1995), cell electroporation, U.S. Pat. No. 5,501,662 (1996); U.S. Pat. No. 5,273,525 (1993), and microinjection, U.S. Pat. No. 5,114,854 (1992). Each of the above-listed methods has specific disadvantages and limitations. The most widely studied gene transfer carriers are viral vectors, including retrovirus, adenovirus, adeno-associated virus, and herpes virus systems. Viral vectors have shown a high transfection efficiency compared to non-viral vectors, but their use in vivo is severely limited. Their drawbacks include targeting only dividing cells, random insertion into the host genome, risk of replication, and possible host immune reaction. J. M. Wilson, 96 J. Clin. Invest. 2547-2554 (1995).
Compared to viral vectors, nonviral vectors are easy to manufacture, less likely to produce immune reactions, and will not produce replication reactions. Dimethylaminoethyldextran-, calcium phosphate- and polycation-mediated transfection procedures have been used for tissue culture cells in the laboratory. Under some conditions, transfection efficiencies of close to 100% of the cells have been obtained in vitro. In general, however, nonviral vectors have been found to be ineffective for in vivo introduction of genetic material into cells and have resulted in relatively low gene expression. Various cationic amphiphiles have been extensively investigated and added to liposome formulations for the purpose of gene transfection. F. D. Ledley, 6 Human Gene Therapy 1 129-1144 (1995). To date, a cationic lipid system has been regarded as the most promising DNA transfection protocol, because it overcomes the problems with using viral vectors. However, transfection efficiency using cationic lipids is still not as high as with viral vectors, and complaints about cytotoxicity have been raised. Therefore, continuing investigation is required to find a new gene transfer protocol.
In view of the foregoing, it will be appreciated that development of a gene delivery system for in vivo use that is both safe and efficient would be a significant advancement in the art.